package UDPDemo;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;

public class UDPEchoServer {
    private DatagramSocket socket = null;

    public UDPEchoServer(int port) throws SocketException {
        this.socket = new DatagramSocket(port);
    }

    public void start() throws IOException {
        System.out.println("服务器启动");

        while (true) {
            DatagramPacket requestPacket = new DatagramPacket(new byte[4096], 4096);

            socket.receive(requestPacket);

            String request = new String(requestPacket.getData(), 0, requestPacket.getLength());

            String response = process(request);

            DatagramPacket responsePacket = new DatagramPacket(response.getBytes(), 0, response.getBytes().length,
                    requestPacket.getSocketAddress());

            socket.send(responsePacket);

            System.out.printf("[%s, %s] request: %s, response: %s\n", requestPacket.getAddress(), requestPacket.getPort(), request, response);
        }
    }

    public String process(String request) {
        return request;
    }

    public static void main(String[] args) throws IOException {
        UDPEchoServer udpEchoServer = new UDPEchoServer(9090);
        udpEchoServer.start();
    }
}
